In recent years, as semiconductor processes become finer, transfer patterns for use in photolithography of semiconductor processes have rapidly become finer. In the next generation, micro-fabrication at 20 nm or less would be demanded. It is thus expected to develop an exposure apparatus in which an extreme ultraviolet (EUV) light generating apparatus for generating extreme ultraviolet light at a wavelength of approximately 13 nm is combined with a reduced projection reflective optical system.
Three types of EUV light generating apparatuses have been proposed, which include an LFP (laser produced plasma) type apparatus using plasma generated by irradiating a target with a laser beam, a DPP (discharge produced plasma) type apparatus using plasma generated by an electric discharge, and an SR (synchrotron radiation) type apparatus using synchrotron radiation.
Patent Document 1: Japanese Patent Application Publication No. 2010-239039 A
Patent Document 2: Japanese Patent Application Publication No. 2012-042630 A